Method and system for autonomous vehicle speed following

Abstract

In one embodiment, an autonomous driving vehicle (ADV) speed following system determines how much and when to apply a throttle or a brake control of an ADV to maneuver the ADV around, or to avoid, obstacles of a planned route. The speed following system calculates a first torque force to accelerate the ADV, a second torque force to counteract frictional forces and wind resistances to maintain a reference speed, and a third torque force to minimize an initial difference and external disturbances thereafter between predefined target speed and actual speed of the ADV over a planned route. The speed following system determines a throttle-brake torque force based on the first, second, and third torque forces and utilizes the throttle-brake torque force to control a subsequent speed of the ADV.

What is claimed is: 
     
       1. A computer-implemented method for controlling a speed of an autonomous vehicle, the method comprising:
 calculating, by one or more processors, a first torque force for accelerating the autonomous vehicle to autonomously maneuver the autonomous vehicle, including:
 determining a first speed representing a target speed of the autonomous vehicle to maneuver the autonomous vehicle at a first reference time, 
 determining a second speed representing a target speed of the autonomous vehicle to maneuver the autonomous vehicle at a second reference time; and 
 calculating the first torque force based on the first and second speeds in view of a throttle control command delay; 
 
 converting the first torque force into a throttle command, wherein the throttle command is based at least on the first torque force and the throttle control command delay, wherein the throttle control command delay is longer than a brake control command delay; 
 calculating, by the one or more processors, a second torque force for maintaining a constant speed of the autonomous vehicle; 
 determining, by the one or more processors, a throttle-brake torque force based on the first torque force and second torque force; and 
 controlling, by the one or more processors, a subsequent speed of the autonomous vehicle based on the throttle-brake torque force. 
 
     
     
       2. The method of  claim 1 , wherein calculating the first torque force based on the first and second speeds comprises:
 calculating a speed difference between the first speed and the second speed; and 
 dividing the speed difference by a time difference between the first reference time and the second reference time. 
 
     
     
       3. The method of  claim 1 , wherein calculating the second torque force comprises:
 determining a current speed of the autonomous vehicle; 
 determining a frictional force acting on the autonomous vehicle; 
 determining a wind resistance acting on the autonomous vehicle; and 
 calculating the second torque force required to maintain the current speed of the autonomous vehicle based on the current speed, the frictional force, and the wind resistance. 
 
     
     
       4. The method of  claim 3 , wherein the wind resistance is determined based on a second order of the current speed, wherein the frictional force is determined based on a first order of the current speed. 
     
     
       5. The method of  claim 1 , further comprising calculating a third torque force to minimize a speed difference between an actual speed and a target speed of the autonomous vehicle, wherein the throttle-brake torque force is determined further based on the third torque force. 
     
     
       6. The method of  claim 5 , wherein calculating the third torque force comprises:
 determining the target speed of an autonomous vehicle; 
 determining the actual speed of the autonomous vehicle; and 
 calculating the third torque force required to minimize the speed difference between the target speed and actual speed using a proportional-integral-derivative (PID) controller. 
 
     
     
       7. The method of  claim 5 , wherein calculating the throttle-brake torque force comprises summing the first, second, and third torque forces. 
     
     
       8. A non-transitory machine-readable medium having instructions stored therein, which when executed by a processor, cause the processor to perform operations of operating an autonomous vehicle, the operations comprising:
 calculating a first torque force for accelerating the autonomous vehicle to autonomously maneuver the autonomous vehicle, including:
 determining a first speed representing a target speed of the autonomous vehicle to maneuver the autonomous vehicle at a first reference time: 
 determining a second speed representing a target speed of the autonomous vehicle to maneuver the autonomous vehicle at a second reference time; and 
 calculating the first torque force based on the first and second speeds in view of a throttle control command delay; 
 
 converting the first torque force into a throttle command, wherein the throttle command is based at least on the first torque force and the throttle control command delay, wherein the throttle control command delay is longer than a brake control command delay; 
 calculating a second torque force for maintaining a constant speed of the autonomous vehicle; 
 determining a throttle-brake torque force based on the first torque force and second torque force; and 
 controlling a subsequent speed of the autonomous vehicle based on the throttle-brake torque force. 
 
     
     
       9. The non-transitory machine-readable medium of  claim 8 , wherein calculating the first torque force based on the first and second speeds comprises:
 calculating a speed difference between the first speed and the second speed; and 
 dividing the speed difference by a time difference between the first reference time and the second reference time. 
 
     
     
       10. The non-transitory machine-readable medium of  claim 8 , wherein calculating the second torque force comprises:
 determining a current speed of the autonomous vehicle; 
 determining a frictional force acting on the autonomous vehicle; 
 determining a wind resistance acting on the autonomous vehicle; and 
 calculating the second torque force required to maintain the current speed of the autonomous vehicle based on the current speed, the frictional force, and the wind resistance. 
 
     
     
       11. The non-transitory machine-readable medium of  claim 10 , wherein the wind resistance is determined based on a second order of the current speed, wherein the frictional force is determined based on a first order of the current speed. 
     
     
       12. The non-transitory machine-readable medium of  claim 8 , wherein the operations further comprise calculating a third torque force to minimize a speed difference between an actual speed and a target speed of the autonomous vehicle, wherein the throttle-brake torque force is determined further based on the third torque force. 
     
     
       13. The non-transitory machine-readable medium of  claim 12 , wherein calculating the third torque force comprises:
 determining the target speed of an autonomous vehicle; 
 determining the actual speed of the autonomous vehicle; and 
 calculating the third torque force required to minimize the speed difference between the target speed and actual speed using a proportional-integral-derivative (PID) controller. 
 
     
     
       14. The non-transitory machine-readable medium of  claim 12 , wherein calculating the throttle brake torque force comprises summing the first, second, and third torque forces. 
     
     
       15. A data processing system, comprising:
 a processor; and 
 a memory coupled to the processor to store instructions, which when executed by the processor, cause the processor to perform operations of operating an autonomous vehicle, the operations including: 
 calculating a first torque force for accelerating the autonomous vehicle to autonomously maneuver the autonomous vehicle, including;
 determining a first speed representing a target speed of the autonomous vehicle to maneuver the autonomous vehicle at a first reference time, 
 determining a second speed representing a targets peed of the autonomous vehicle to maneuver the autonomous vehicle at a second reference time, and 
 calculating the first torque force based on the first and second speeds in view of a throttle control command delay, 
 
 converting the first torque force into a throttle command, wherein the throttle command is based at least on the first torque force and the throttle control command delay, wherein the throttle control command delay is longer than a brake control command delay, 
 calculating a second torque force for maintaining a constant speed of the autonomous vehicle, 
 determining a throttle-brake torque force based on the first torque force and second torque force, and 
 controlling a subsequent speed of the autonomous vehicle based on the throttle-brake torque force. 
 
     
     
       16. The system of  claim 15 , wherein calculating the first torque force based on the first and second speeds comprises:
 calculating a speed difference between the first speed and the second speed; and 
 dividing the speed difference by a time difference between the first reference time and the second reference time. 
 
     
     
       17. The system of  claim 15 , wherein calculating the second torque force comprises:
 determining a current speed of the autonomous vehicle; 
 determining a frictional force acting on the autonomous vehicle; 
 determining a wind resistance acting on the autonomous vehicle; and 
 calculating the second torque force required to maintain the current speed of the autonomous vehicle based on the current speed, the frictional force, and the wind resistance. 
 
     
     
       18. The system of  claim 17 , wherein the wind resistance is determined based on a second order of the current speed, wherein the frictional force is determined based on a first order of the current speed. 
     
     
       19. The system of  claim 15 , wherein the operations further comprise calculating a third torque force to minimize a speed difference between an actual speed and a target speed of the autonomous vehicle, wherein the throttle-brake torque force is determined further based on the third torque force. 
     
     
       20. The system of  claim 19 , wherein calculating the third torque force comprises:
 determining the target speed of an autonomous vehicle; 
 determining the actual speed of the autonomous vehicle; and 
 calculating the third torque force required to minimize the speed difference between the target speed and actual speed using a proportional-integral-derivative (PID) controller. 
 
     
     
       21. The system of  claim 19 , wherein calculating the throttle-brake torque force comprises summing the first, second, and third torque forces.